1. Field of the Invention
The invention relates to a technical field of a power supply system including a plurality of electrical storage means.
2. Description of Related Art
There is known a power supply system including a first electrical storage device, a second electrical storage device and a converter that distributes electric power between these first electrical storage device and second electrical storage device (see, for example, Japanese Patent Application Publication No. 2009-261183 (JP 2009-261183 A)). The first electrical storage device and the second electrical storage device each are, for example, a rechargeable direct-current power supply, such as a secondary battery and a capacitor. Particularly, a power supply system described in JP 2009-261183 A determines a distribution ratio in the following manner. The distribution ratio is the ratio of electric power that is distributed to the first electrical storage device and electric power that is distributed to the second electric storage device. Specifically, the power supply system described in JP 2009-261183 A, when the first electrical storage device and the second electrical storage device are charged, determines a distribution between an electric power that is charged into the first electrical storage device and an electric power that is charged into the second electric storage device (distribution ratio) on the basis of the ratio of an available charge energy of the first electrical storage device and an available charge energy of the second electrical storage device. Each available charge energy is a parameter that is calculated on the basis of a difference between a charge state value (SOC) indicating a current state of charge of the corresponding electrical storage device and a charge state value of the corresponding electrical storage device at the timing at which an electric power (Win) that is chargeable into the corresponding electrical storage device begins to be limited. Similarly, the power supply system described in JP 2009-261183 A, when the first electrical storage device and the second electrical storage device are discharged, determines a distribution between an electric power that is discharged from the first electrical storage device and an electric power that is discharged from the second storage device (distribution ratio) on the basis of the ratio of an available discharge energy of the first electrical storage device and an available discharge energy of the second electrical storage device. Each available discharge energy is a parameter that is calculated on the basis of a difference between a current charge state value of the corresponding electrical storage device and a charge state value of the corresponding electrical storage device at the timing at which an electric power (Wout) that is dischargeable from the corresponding electrical storage device begins to be limited.